Robots and Welding

Robotic considerations for optimizing laser welding and cutting


Facilitating the continued growth of the robotic welding market, laser technologies continue to compliment high-performance industrial robots, bringing relevant welding processes to fruition for the manufacturing sector. From heat conduction welding and deep penetration (a.k.a. keyhole) welding to hybrid laser arc welding, advanced technologies are enabling the creation of strong, repeatable weld seams at relatively high speeds with amazing precision.

Ideal for medium- to large-volume production runs, the process for robotic laser welding uses a focused laser beam rather than a traditional electrical arc. The beam power control offers precision heat input and targeting of weld seams, making it ideal for a wider variety of metal types and precision parts. Moreover, materials once seen as non-weldable are now being used to fulfill unique consumer demands. Dissimilar sheet metals, for example, are often used by electric vehicle (EV) manufacturers to produce battery trays and motor mounts, further accelerating market growth.

Industry 4.0 and the adoption of advanced technologies, including highly reliable robots and their peripherals, are making this a reality. This is especially true for rigid robots designed specifically for the precise demands of laser welding, and laser cutting for that matter.

Robot considerations

To complete the required task, most laser welding robots need a high repeatability factor or the ability to consistently reach a specified point. Interrelated with accuracy – the measure of error between the target point and the actual point – repeatability dictates the presence of rigidity.

For example, with MIG welding, the user aims for a robot repeatability of half the filler metal (weld wire) width. If using the most common weld wire size at 0.045 in., the robot needs to be repeatable to the weld joint by 0.0225 in. (or 0.5 mm). In contrast, a laser can be focused as small as a 0.1-mm spot in autogenous laser welding without filler metal. So, if abiding to a similar rule of thumb, the user would want a robot with 0.05-mm repeatability to consistently laser weld with the given precision heat input.

However, lasers also offer “wobble” features that increase the effective width of the weld area to aid in needed precision or even gap coverage. Regardless, tolerances for the weld and the part become much tighter.

Robots such as Yaskawa’s GA50 are designed with higher precision gear reducers and precisely matched servo motors to be capable of delivering the high path accuracy needed for laser welding tasks.

Robots of this caliber, such as the Yaskawa GA50, are built with higher precision gear reducers and precisely matched servo motors, offering the high path accuracy needed for laser welding. It is important to note, however, these robots are already very repeatable (±0.015 mm), so they matter most when the robot is moving during the welding process.

If the application in question does not require the robot to move during welding, it is possible to use a less specialized robot where rigidity is concerned. This is enabled by using a higher payload capacity robot that can successfully handle a remote laser head, typically weighing 30 kg to 50 kg.

Ideal for overcoming common laser welding challenges, like welding dissimilar metals or highly reflective metals such as aluminum and copper, laser or wobble heads are designed with multiple moving parts. From complete seam tracking systems that can automatically adjust the weld location to match seam positions to utilizing high-speed vision with integrated LED lighting, remote laser heads combine innovative technologies to provide process consistency.

Enabling easy access to parts in enclosed or tight spaces, a laser welding robot typically requires access to a single side of the part.

This allows the robot to fix on a designated position, while the process head focuses and moves the laser on its own (or the robot and laser can both move for longer welds).

Optimizing production

With peripheral technology in mind, remote laser heads utilize special software, which allows programs to operate while the robot is moving. This is known as welding “on the fly” and is well-suited for a smaller number of applications. More common is the use of an OEM robot control interface that is compatible with most laser head brands. Here, basic welding parameters can be set as well as controlling figures on a remote laser head.

While most robots are streamlined for their given application and considered to be space-saving, different laser heads offer unique advantages. There are certainly some advantages to fiber laser systems with smaller heads – with the main advantage being weld speeds that allows for larger parts with greater throughput (because contact does not have to be made with the part in most remote laser applications).

While hybrid laser welding would not be included here, the idea of being able to access very tight areas while the laser head is away from the part (100+ mm away) is quite appealing for certain tasks where autogenous welding can be utilized.

Today’s state-of-the-art laser systems boast numerous safety features, such as lighttight enclosures, interlocked barrier systems and perimeter safeguarding.

Regardless of the robot or laser head chosen, the use of more affordable and capable laser technologies with high-performance industrial robots and part positioners provides manufacturers with the perfect mix of tools for optimizing production. Aside from extremely fast cycle times, high repeatability and remarkable precision, robotic laser welding offers several other notable perks:

  • Easy part access – a laser welding robot typically only needs access to one side of the part, making it possible to weld in tight or enclosed areas, or even in place of spot welding through seam stepper technologies
  • Fast process speed – a robot equipped to laser weld offers exceptionally fast axis speeds and acceleration capabilities to reduce cycle time, increasing product throughput up to 10 times.
  • High-quality welds – this very precise method excels where high aesthetics are required. Thin-gauge parts requiring continuous seams with zero spatter for “clean” welds are easily processed. The option of having a lack of filler metal makes gap tolerances tight, reducing the number and type of joints needed.
  • Increased user safety – laser systems today are peppered with safety features such as light-tight enclosures, including interlocked barrier systems and perimeter safeguarding.
  • Dedicated interface and calibration – as mentioned, most laser welding equipment has a dedicated interface to a standalone laser controller, providing the ability to modify weld shape, power and frequency.

Cutting similarities

Similar to laser welding, the process of laser cutting also relies heavily on accuracy and rigidity. Ideal for cutting small holes and sharp corners or even plasma cutting, flexible automated laser cutting solutions for 2-D and 3-D cutting are effectively helping to overcome challenges of conventional laser cutting machines. From being able to position the laser cutting head in almost any position and orientation within a workspace to being able to cut non-ferrous and thick materials with ease, high-performance industrial robots help to cut complex shapes efficiently and sustainably with precise detail.

Like laser welding, cutting robots also rely on sophisticated software for the utmost precision – especially if the target for path accuracy is to be within 0.1 mm with a 30-kg payload. OEMbrand versions, such as Yaskawa’s Formcut, help to automatically generate an ideal path to cut shapes based on user-specific geometry. Circle, rectangle, ellipse, pentagon and 2-D hexagon shapes are typically supported, with easy definition of shape size and rotation from a single programmed point. Parameters, such as the cut motion start and overlap, robot speed, timing options and corner radii can often be defined in the cut file.

As the overall demand for automation increases, more precision part welding will be accomplished by the likes of laser welding. Similarly, the growing number of handheld laser welding guns infiltrating the market will prompt greater use of collaborative robots for this task. The built-in safety from these handheld guns does not require a lighttight enclosure and adds to the userfriendly appeal of cobots.

While laser welding and cutting can be difficult to master for robot programmers, intelligent tools are helping to ease the path to productivity.

Manufacturers on the fence about the use of automated laser technology should reach out to local robot suppliers or integrators to learn more about the production possibilities.

Yaskawa Automation Inc.

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